Picosecond Transient Absorption Spectroscopy System

picoTAS

Unisoku has been developing this product in cooperation with Nihon University, Osaka University and Meijo University in theframework of the Japan Science and Technology Agency’s “Development of Systems and Technologies for Advanced Measurement
and Analysis (JST-SENTAN)” program.
The contents of this catalog are subject to change without prior notice for improvement.
Reproduction or copying the contents of this catalog in part or whole is prohibited without permission of Unisoku.

UNISOKU Co., Ltd

2-4-3 Kasugano, Hirakata, Osaka 573-0131, Japan
TEL: +81-72-858-6456 / FAX: +81-72-859-5655

Catalog No.
UBPT 2018-05A

picoTASCan Easily Measure Short-Lived Intermediates.

Features Completely Covers Gap Time Region (1 ns ~ 20 ns)

In most of light induced phenomena, intermediates (transient species) play
important roles to determine reaction efficiency and final products, and single
reaction cycle often involves multiple intermediates which are observed in different
time and wavelength regions.

picoTAS can observe light absorption of these intermediates in wide range oftime and wavelength. Therefore, picoTAS can contribute to various researches ofrapid reactions and development of high-performance materials and devices.

 Measures Wide Time Range from 100 ps to s
 Broadband Wavelength Coverage from VIS to NIR Removes Fluorescence Signal
 Asynchronous Operation
 Compact Size / No Optical Bench Required (-ns model)
What is Transient Absorption Spectroscopy (TAS) ?
• Fast Time Resolved Absorption
Measurement• Detects and Identifies Short-Lived
Intermediates• Both Non-Luminescent andLuminescent Intermediates aredetectable• Explores and Analyzes Multi-stepComplex Processes

Transient Absorption Spectroscopy (TAS) is a methodof first time-resolved absorption measurement. A
pulsed light (pump light) induces reactions of atarget sample, then subsequent processes areobserved by absorption change of probe light.
It is known that fluorescence lifetime measurement isalso a time resolved method, but information
obtained is limited to a fluorescent process at thefirst stage of the reaction (excited singlet state). On
the other hand, information about non-fluorescentprocesses in a wide time region (short-lived radicalspecies, charge transfer states, etc.) can be obtainedby TAS, so we can explore and analyze multi-stepcomplex processes.

What is the Difference between
picoTAS and Conventional Techniques?
picoTAS
fspsnsPump and Probe Method

2μs

mss

Nanosecond
FlashPhotolysis
methodNanosecond
Flash
Photolysis
methodGap Time Region

There are mainly two conventional transientabsorption (TA) techniques, Pump & Probe
method and Nanosecond Flash Photolysis
method. However these methods havedifficulty in measuring the time region from 1
to 20 nanoseconds in which many importantphenomena exist.
picoTAS can measure wide time range including
this “Gap Time Region” (1 ‐ 20 nanoseconds)
where conventional methods have hardlyobserved. In addition, picoTAS has a capabilityof eliminating the influence of fluorescence,
therefore, not only non-fluorescent but also
fluorescent intermediates can be detected andidentified correctly which have never beenobserved so far.

Wide Applications
Fluorochrome-Labeled DNA Photochromism Optical Switching
Target Quantum-Dot
Phenomena Artificial Photosynthesis
 Photocatalyst
 Organic Solar Cell, etcTargetAreas

TargetSamples

Fullerene
Porphyrin
Photoreactive OrganicMolecule
Various Metal Complex
Titanium Dioxide
Organic EL Device
Carbon Nanotube, etc.









TargetFields

Excited Singlet State
Triplet StateElectron Transfer
Charge Separation
Radical Formation
Excimer Formation
Energy Transfer, etc.

Photochemistry
Photophysics
Photobiology
Nanoscience
Materials Chemistry
Energy Science
Environmental Science,etc.

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picoTAS System Configuration
Models – Coverage of Time and Wavelength
1600 nmpicoTAS Optical Unit
・ 410 – 1600 nm

800 nmNIR(Monochrometers, Optics, Sample Chamber, Detectors)
PC

optical design minimizing chromatic aberration

・ Double Beam Optical Systemhigh excitation efficiency for thin samples

・ Automatic shutter (pump, probe)
・ Probe Light Auto-Balancing Mechanism

400 nm

・ 2 mm Solution Cell Holder
・ Thin Film Holder
・ Oblique Incidence Excitation

VIS

corrects light intensity fluctuation

Dedicated
Oscilloscopepsns-ps (picosecond)modelµss

ms-ns (subnanosecond)model

Photonic Crystal Fiber

Probe Light Source

Pump Light Source

High-Repetition-Rate Super Continuum Light Source
50-100 ps, 20 MHz, 410-1600 nm-ns model : Pulse Width 350 ps, 1 kHz
OR-ps model : Pulse Width 25 ps, 1 kHz

Pump Light and Probe Light of picoTAS are Asynchronous
Principle: Randomly Interleaved Pulse Train (RIPT) Method
Pump 1st time

In the RIPT method, signal waveforms of both pump light and probe light are recorded by highspeed detectors on each pump light irradiation. The delay time of a probe pulse just after the pumppulse is calculated from these waveforms. Each light intensity of probe light pulse that is transmitted
through a sample is recorded by using a detector with amplifier, and the intensity is plotted basedon the delay time. When pump light irradiation is repeated, the delay time differs every time
because pump light and probe light are asynchronous. In this way, the plot generates a continuous

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curve after many-time pump light irradiation. By executing delta optical density calculation, transientabsorption curve is reconstructed.

Pump 2nd time

Optics Letters, 41, 1498 (2016)

Pump kth timeHighlighted in Nat. Photon., 10 (2016), 285
and Science, 352 (2016), 669.

PumpProbe

Reconstructed windowt d [1]Detected
Signalt d [2]t d [k]I
Delta Optical Density
Calculation

td5

Completely Covers Gap Time Region (1 ns ~ 20 ns)

Broadband Wavelength Coverage from VIS to NIR

The conventional methods have difficulty in measuring from 1 to 20

Recently, near-infrared measurements in transient absorption spectroscopy
are highly demanded. As picoTAS uses a super-continuum light source

which has almost never been studied so far.
Benzophenone in Acetonitrile
Probe at 550 nm

In the Gap Time region, there exists various states andprocesses inside and among molecules.
“Excited Singlet State”
the initial excited state of many photochemical reaction“Excited Triplet State”
the second excited state which plays a key role indetermining the reaction products“Radical Species”
highly reactive intermediate statefor the probe light source, a broad wavelengths range from visible (> 410nm) to near-infrared region (< 1600 nm) can be covered seamlessly.

Obtain Transient Absorption
Temporal Profile
at Every Wavelength

Gap Time Region
Pump & Probe

nsFP

picoTAS

picoTAS

Observable
Phenomena

Intersystem
Crossing (ISC)

Excited Triplet

Radical Formation, Electron Transfer, etc.

Gap Time Regionfsps

Wave length
Spectrum power density

Excited Singlet

Nanosecond Flash Photolysis(nsFP)

Spectrum power density

nanoseconds, but picoTAS allows us to measure this “Gap Time Region”

Broadband
Wavelength
Coverage from VIS to NIR
µss
msns

Pump & Probe

Measures Wide Time Range from 100 ps to ms

Select Time to Extract
Transient Absorption Spectra

Super-continuum light source used as theprobe light source in picoTAS emits light in a
broad wavelength range from visible to nearinfrared region. Though its light intensity has
wavelength dependence, picoTAS can adjust
the light intensity automatically which enters
into detectors.

Display and Save the Spectra

picoTAS can measure a wide time range. It covers more than 6 orders ofmagnitude from 100 picosecond to millisecond, from formation to full decayof intermediates.
C60 in TolueneIr(ppy)3 in THF

Future Prospect
By combination with picosecond probe light sources of infrared or X-ray region,

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studies of wider wavelength region (energy region) can be realized.

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picoTAS

Data Example

Removes Fluorescence Signal
In conventional nanosecond flash photolysis measurements, luminescence fromthe sample often interferes with the signal. Since picoTAS has an ingenious

way to remove luminescence signal, we can obtain accurate transient absorption(TA) signal of excited singlet and triplet, etc.

picoTAS

Conventional nanosecond
Flash Photolysis

Comparison of Time Resolution（10-90% Rise Time）
picoTAS has 100 times higher time resolution than conventional nanosecond flash photolysis systems. Thetime resolution (<100 ps for -ps model, <400 ps for -ns model) is comparable to TCSPC fluorescence lifetime
measurements, so picoTAS can be widely applied to many reactions including non-luminescent samples.

picoTAS-ps model<100 pspicoTAS-ns model<400 ps

Typical Data fornanosecond Flash Photolysis～ 10 nsfluorescence
Observation of the fast (<10 ps ) ISC of palladium porphyrin

Figure Courtesy of Dr. T. Suenobu, Osaka Univ.

Accurate TA signals without fluorescence

TA signals covered by fluorescenceHigh Sensitive Transient Absorption
Measurement of Photocatalyst
To elucidate the photoreaction mechanism of titanium dioxide
which shows remarkable behavior as a photocatalytic material, it
is known that the pump light intensity must be reduced anddetection of very small TA signals is required. In thismeasurement, picoTAS catches less than 1 mOD changes(equivalent to 0.025% transmittance change) in nanoseconds
time region.

fluorescence

TA spectrum covered by fluorescence

Accurate TA spectra without fluorescence

Luminescence Signal Removal in picoTAS
IntheRIPT

methodusedinpicoTAS, by picking up the signal

8intensity just before the rise ofeach probe pulse signal andrepeating this procedure for aseries of pulse train data set, abaseline
curveincludingluminescence such as fluorescenceand phosphorescence can bereconstructed. By subtracting thebaseline curve from individual
probe pulse train data, and thenpicking up probe light intensity,
pure TA signals, where emission
signals are removed, can beobtained.

1Samples Courtesy of Prof. R. Katoh, Nihon Univ.

Fullerene (τ ISC ≃ 1 ns)
Fullerene is an promising material for electron acceptors of organic thinfilm solar cell and its time constant of intersystem crossing (ISC) isknown ~1 ns, so it is difficult to measure TA of this attractive reagent byboth pump & probe and nanosecond flash photolysis methods. With theuse of picoTAS, the spectra of the excited singlet, ISC and triplet state
can be clearly observed from visible to infrared wavelength region. Also,a complete decay curve of the triplet with lifetime of microseconds canbe observed.

ISCPump 355 nm, 25 ps
500 nm～1250 nm

1at 900 nm

Minimum Bin 50 ps

Tn←T1Sn←S1

S1 decay9Specifications
ModelpicoTAS-nsMethodTime Resolution (10%-90% Rise Time)
Delay Time Resolution
Time Window
Wavelength Range
Automatic Control
Sample Holder
Light Source
Pump LightProbe Light

PC &Software

picoTAS-ps

RIPT method (Randomly Interleaved Pulse Train method)<400 ps<100 ps

10 ps, 20 ps, 50 ps, 100 ps, 200 ps, 500 ps, 1 ns, 2ns, 5 ns, 10 ns, 20 ns

100 ns ～ 2 ms
410 ～ 1600 nm
Wavelength Scan, Light Intensity Adjustment, Shutter ControlSolution （Optical Path Length of 2mm）、Thin Filmpicosecond Mode-Locked Laserpassive Q-SW Microchip Laser
532 nm and/or 355 nm
532 nm and/or 355 nm
and/or 266 nm<350 ps<25 ps>20 μJ>80 μJ
100 - 1000Hz （variable）
1000 Hz
Picosecond Supercontinuum Light Source<50-100 ps （dependent on wavelength）
20 MHz ± 5%
Windows 7/10

Wavelength
Pulse Width
Pulse Energy
Repetition Rate
Light Source
Pulse Width
Repetition RateOS

Automatic Reconstruction of Transient Absorption Temporal Profile,
Conversiont to Transient Absorption Spectra, Curve Fitting (Nonlinear Least
Square method), Data Storage in Text Format

Function

Installation Environment

No Optical Bench Required

On Optical BenchpicoTAS Models (Coverage of Time and Wavelength)“Gap Time Region”
Difficult to Measurewith ConventionalMethods

1600 nmPump & Probe Method

Nanosecond Flash
Photolysis Method

680
Top View
pump light source
installation spacefor -ns model

480

Installation spaces for probe light source, PC andoscilloscope are needed separately.
-ps model further requires an installation space forpump light source.

Back View

Front View
225

Options

Wavelength-Tunable Pump
Light Source for -ps model
Excitation Wavelength Can be
Varied.
Type

Optical Parametric Generator (OPG)

Pump Laser

Picosecond mode-locked laser 1kHz, 355
nm, 0.3W

Wavelength Range

410-709 nm, 710-2300 nmPulse Energy

50µJ@450nm

CoolSpeK Low-Temperature Cell
Holder (for 2mm cell)pump light source
installation spacefor -ns model

Customization
We will construct a customized system withexisting pump source, probe source in your lab.
Recommended
Specification
for Pump Light
SourceRecommended
Specification
for Probe LightSource

800 nmNIR
VIS

Temperature Range-80℃ ～ Room Temperature（~100°C）

Temperature Control

Flow control of liquid nitrogen by anautomatic valve

Functions

Low Dew Condensation by Heating of
Optical Window, Stirrer

Liquid Nitrogen
Reservoir

Stainless, 2L
Duration of 2H at -80℃

Global Analysis Software
400 nmSpectrum Analysis of Multicomponent
and Various Analysis Functions

psns-ps（picosecond）
modelµs

mss-ns（subnanosecond)modelSoftware

AnalysisFeatureOS

Repetition rate
Pulse width
Output energy

1 kHz,<500 ps,
20 μJ/pulse※Please contact us for the source out of
the specification above① Supercontinuum light source withrepetition-rate of 20 MHz② Supercontinuum light source equippedwith a pulse picker (Settable at 20MHz. ）③ Picosecond laser diode with highoutput energy (100nJ/pulse)

Temperature Range from -80°C to+100°C

fs10Dimensions of Optical Unit

Notes: System performance might be limited depending on thespecifications of pump light source and/or probe light source.

■ Single Wavelength Measurement by
Picosecond Diode Laser
Probe LightSource

Picosecond Diode Laser

Wevelength (nm)450, 532, 1000, 1100, 1200, 1300, etc.

Pulse Width

Dependent on Light Source Selected
200 ps@532 nm, 50 ps@1000 nm, etc

Globalworks - made by US Company OLIS
Singular Value Decomposition (SVD),
Global Fitting
Lifetime Calculation, Selection of Reaction
Mechanism Model
Windows XP/7

■ Please feel free to contact us for the transientabsorption system that can eliminate long-lived
luminescence by making the most use of the RIPT
method and a lower repetition-rate supercontinuum
light source.

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